|Party|Leader|From|To|
|---|---|---|---|
|Scottish National Party|Gordon Wallace|May 1974|May 1978|
|Scottish National Party|Robert Cunning|May 1978|May 1980|
|Labour|(?)|May 1974|May 1980|
|Labour|Iain Nicolson|May 1980|May 1984|
|Labour|Charles Kennedy|May 1984|Jan 1989|
|Labour|Andrew Cochrane|Jan 1989|May 1992|
|Labour|Robert Coyle|May 1992|May 1993|
|Labour|Brian Wallace|Jun 1993|Sep 1994|
|Labour|Charles Kennedy|Sep 1994|Apr 1996|
|Conservative|William Leslie (?)|May 1974|May 1992|
|Conservative|Ian Young|May 1992|April 1996|
|SDP/Liberal Alliance|Joyce Shannon|February 1986|May 1992|
|Independent|Andrew Archibald|May 1974|May 1977|

Question: how many parties had the same leader in office twice?
Answer: 1